We all know arguing against a strongly held opinion usually results in the person with the strong opinion digging their heels in even deeper. At that point, things like reason kind of go by the wayside and don't have much effect.
As a poor example, my mother has fully bought into a snake-oil scheme where they sell you concentrated hydrogen peroxide as a cure-all. She won't hear a word against it, she always brings the conversation back to "OTC hydrogen peroxide has stabilizers in it." Asking "what is a stabilizer" gets no response.
The truth is, she doesn't know what a stabilizer is, but it's plausible enough to her that they could be "bad" that she's willing to buy the rest of the farm, along with the cow.
How can you argue against that kind of strongly held opinion? When the other party won't listen because of how strongly held the opinion is, you might as well talk to a wall.